During the last 13 years our group has studied the development of hyperlipidemia and atherosclerosis induced experimentally in dogs and rhesus monkeys by a regimen of thyroid suppression and a diet rich in cholesterol and fat. We have observed enhancement of segmental localization and severity of atheroma in dogs on the atherogenic regimen when submitted to arterial grafting procedures, various types of arterial injury, and various methods of induction of peri-arterial fibrosis and fixation. More recently we have studied methods of ameliorating and preventing experimental hyperlipidemia and atherosclerosis. Distal intestinal by-pass has emerged as the most effective surgical method used to date in both dogs and rhesus monkeys. Controlled studies are in progress in our laboratory in both dogs and monkeys designed to compare distal intestinal by-pass with other surgical and pharmacologic measures aimed at both prevention and correction of hyperlipidemia and athersclerosis. The present proposal is an outgrowth of controversy concerning the atherogenic susceptibility of autologous venous grafts and the question as to why the venous system generally escapes atherosclerosis. We wish to use the standardized atherogenic dietary regimen in dogs to assess the atherogenic susceptibility of (a) an autologous arterial segment implanted in the venous system, and of (b) an autologous venous segment implanted in the arterial system. Assessment of the gross severity and distribution of atheromatous lesions in grafts and host vessels over 12 to 24 months is proposed as well as attempts to delineate the early lesions of experimental atherosclerosis in these same vessels by light microscopy. The atherogenic potential of the various grafts and host vessels has practical clinical importance. Further, we hope these studies may provide basic information concerning the role of the cellular structure of arterial and venous walls in atherogenesis and evidence as to the validity of the "filtration" theory of atherogenesis.